Nick Buckles, the Chief Executive of G4S, will be called upon today by the Home Affairs Select Committee.
He will be asked explain the "omnishambles" of his company's arrangements for security for the Olympic Games.
The private security company failed to employ enough people despite its
reassurances, so 3,500 soldiers and police from forces around the
country are being drafted in to make up the shortfall.
G4S had repeatedly assured ministers it would "overshoot" its recruitment targets and only admitted it would fail last week, Home Secretary Theresa May told MPs.
There are also questions about the level of training the G4S staff who will be on duty have received.
MPs on the Home affairs Committee will want to know precisely when G4S realised there was a problem, and when they told ministers and London Mayor Boris Johnson that they would fail to provide the guards they had promised.
The company's contract with the government was worth £284m, but it now stands to lose around £50m, and Mr Buckles has admitted that he may lose his job as a result.
Mrs May said: "G4S only told the Government that they would be unable to meet their contractual arrangements last Wednesday and we took immediate action."
As well as the 3,500 troops, police officers from nine forces have now also been switched to Olympics security duties.
The forces involved are Dorset, Surrey, Hertfordshire, Northumbria, South Wales, Strathclyde, West Midlands, Thames Valley and Greater Manchester.
Assistant Commissioner Chris Allison, the national Olympics security co-ordinator, said: "Forces are making sure they make the best use of their resources locally to do all they can to minimise the impact on local policing."
But West Midlands Police Federation chairman Ian Edwards said it was "chaos, absolute chaos".
Shadow Home Secretary Yvette Cooper said: "It is incomprehensible that with 11 days to go, the Home Secretary still doesn't know how many staff G4S are likely to provide. We all want the G4S shambles sorted out swiftly now. But if even more troops and police are going to be needed, they need to know fast so they can prepare."
Committee Chairman Keith Vaz will want to know why it was that this crisis has come to a head less than two weeks before the Olympics begins when a report by HM Inspectorate of Constabulary warned about concerns over security 10 months ago.
This lead Games organisers to increase the number of security guards to be supplied by G4S from 2,000 to 10,400 while the value of the contract more than trebled from £86m to £284m.
Mr Vaz said: "With a fortnight to go until the Olympics, it is vital that the government has the security situation in hand. The shortfall in security guards provided by G4S and the drafting of armed forces personnel is a shocking development so close to the Games.
"It is vital that the public is safe and not left out of pocket by this debacle."
